Well if you're worried you should talk to him. But he should be respectful about it if he is going to use the Ouija board. I've used one before, and it can actually be fun, especially at night :D And you should also tell him to look more into it, like how to end them, and how to try them respectfully, because trust me, you don't want a pissed off ghost on your hands, that SUCKS. And also if your so worried about him, you should help him out if he does use the Ouija board, since that way you can make sure nothing bad happens to him. Trust me, it'll be fine. I've used an Ouija board a million times, and I'm just fine, so your friend should be too. There's really nothing to worry about, so relax and calm down. But you really should try it, it can be pretty fun :D
Hope this helps ღ
Wow, that's some friend you got there ha ha!